In June 1926 Herbert Wood, deputy-keeper of the public records of Ireland, read a paper to the Royal Irish Academy under the title ‘Letter from Domnall O’Neill to Fineen MacCarthy, 1317’, based on a manuscript (Add. MS 34727, ff 268–9) in the British Museum. The paper was published shortly afterwards as an interesting — perhaps unique — example of a personal communication from one Gaelic lord to another in the era of the Bruce wars. Wood, who obviously had some doubts concerning it, debated in his final paragraphs the case for and against the possibility of forgery before accepting the letter as genuine. But despite the singularity of the letter and the circumstances of its provenance through one person — Thomas O’Sullivan of Middle Temple, London — it has been unquestioningly accepted by historians both general and specialist.
Since 1926 several contemporary and near-contemporary sources of early MacCarthy history have been published, providing evidence which was not readily accessible in Wood’s time. In the light of sources such as these, the authenticity of the letter deserves to be reassessed, and the purpose of this article is to show that the whole document could well have been a fabrication concocted by O’Sullivan.